krita 5.3 nix flake

the new text tools in krita 6 are sick, but the font selector is broken and when i tried to use the 5.3.2.1 appimage the text tool options weren't visible at all

so i wrote a nix flake to build the krita 6 source on qt5 (because krita 5.3 and krita 6 are secretly twins)

the flake is on codeberg and i have no idea if it will help anyone but i hope it does :3 it essentially reverts this nixpkgs commit while still using the (at the time of writing) 6.0.2.1 source